Implantable devices such as drug pumps are in frequent use for delivering drugs or other liquid medications over long periods of time to selected locations in the human body. These devices commonly include a drug reservoir, catheter means connected to the reservoir to transport the drug and a pumping mechanism to propel the drug in some metered or constant flow dosage to the desired location. Over time, the drug in the reservoir becomes depleted and it is necessary to refill the device with a new supply of drug. In order to avoid the need for surgery in order to access and refill the device, it is desirable to have the ability to refill the drug reservoir percutaneously. This is commonly done by providing the drug pump with a resilient resealable reservoir fill port septum which is accessible by injecting a hypodermic needle through the skin and into the septum thereby providing access to refill the reservoir.
In such devices a catheter access port septum may be provided in addition to the reservoir fill port septum. The catheter access port septum is also accessible percutaneously by hypodermic needle. This septum provides direct access to the catheter bypassing the pump and allows a bolus of drug or fluid medication to be administered directly into the body at the site of the catheter.
Although providing a catheter access port septum is both desirable and advantageous a problem can develop if the person refilling the reservoir incorrectly injects the drug into the catheter access port septum instead of the reservoir fill port septum. This results in the drug being administered directly to the body. This may potentially cause an overdose of drug or other serious problems since the drug is meant to be administered by the pump over a period of time.
In the field of implantable drug pumps various devices have been used to enable the reservoir fill port septum to be correctly located. For example, in U.S. Pat. No. 4,286,584 to Sampson et al., an apparatus is disclosed which, when manipulated over the body at the site of the implanted device, produces an energy pattern which designates the location of the septum. In the SynchroMed(.TM.) Infusion System marketed by Medtronic, Inc., the assignee of the present invention, a template is used which is placed over the site of the implanted device to located the septum.
Although these devices are useful in locating the reservoir fill port they do not prevent the occurrence of human error which could result in the drug being injected into the wrong septum. None of the current devices are equipped with any safety feature which would prevent the inadvertent delivery of drug meant for the reservoir into the catheter access port septum. Present devices rely primarily on the physical separation of the septums in order to prevent possible misdelivery of drug.
Therefore, even though there are devices, as mentioned above, which will accurately locate the reservoir fill port if used correctly, the possibility of human error still exists. This error can result in the inadvertent injection of the drug meant for the reservoir directly into the catheter access port septum and into the body. Thus, a need exists for a device or method which would eliminate or at least reduce the possibility of inadvertent injections of drug directly into the catheter access port.